Atherosclerosis and its major clinical manifestation, coronary artery disease (CAD), is the leading cause of death in the western world. Preventive strategies currently focus on controlling risk factors and lipid levels. Substantial residual risk remains high, even when treatment goals are fully met. In humans, monocytes that infiltrate the plaque differentiate into inflammatory macrophages produce proteolytic enzymes that digest extracellular matrix causing plaque rupture. Plaque inflammation is therefore pursued as a therapeutic target to lower the recurrent rates of atherothrombotic events. Nanomedicine offers exciting new possibilities for the treatment of a variety of pathologies by improving the pharmacokinetics and biodistribution of therapeutic agents, while simultaneously decreasing adverse effects and undesired interactions. In the field of atherosclerosis, nanomedicine is still in its infancy, but is expected to provide potentially revolutionary advances in treatment for the most challenging aspects of cardiovascular diseases. Since nanomedicine remains relatively unexplored for atherosclerosis, novel-imaging strategies that allow characterizing this disease, but also allow the quantitative visualization of nanoparticle targeting and efficacy need to be developed. In this project, we propose to develop and utilize PET/MRI technology for the imaging-based evaluation of nanotherapy for the treatment of atherosclerotic plaque inflammation. To that aim, in collaboration with radiochemists at Memorial Sloan Kettering Cancer Center, we have developed 89Zr radioisotope labeling methods for liposomal nanoparticles (LNPs) and high-density lipoprotein (HDL). We will evaluate the nanoreporter technology in a rabbit model of atherosclerosis. Extensive ex vivo imaging and histological techniques will be applied to evaluate the in vivo findings and to unravel the mechanism of action. The specific aims are: Aim 1: To establish the biodistribution and plaque targeting of liposomal nanoparticles of which only a small fraction is labeled with 89Zr. To quantitatively evaluate plaque macrophage targeting and biodistribution of 89Zr-labeled HDL. : To theranostically evaluate the efficacy Aim 2 Aim 3 of 89Zr-labeled and drug-loaded LNPs in atherosclerotic rabbits by PET/MRI. Translation to the clinic is facilitated by the fact that the individual components of all the proposed nanoparticle formulations and the labeling methods are FDA approved. Finally, using nanoparticle formulations to rapidly inhibit vessel wall inflammation and develop imaging technology to monitor their efficacy may have a profound impact on the management of cardiovascular diseases.